The objectives of the double-blind study were to demonstrate the effect of oxandrolone on muscle strength and the progression of weakness in boys with Duchenne's muscular dystrophy during a 6 months treatment period, and to evaluate the safety and tolerability of the drug in this population. This open-label, active therapy extension protocol will allow those boys who received placebo therapy during the first six months of the study to now receive active drug (oxandrolone), with evaluation of its effects. Boys who had received active therapy during the first six months of study will continue receiving oxandrolone, providing evaluation of the longer-term efficacy and safety of this treatment.